PoE vs Low Voltage Power Supplies Cost Compared

Published Jan 23, 2011 05:00 AM
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In this note, we contrast the cost of powering cameras via Power over Ethernet vs a non-powered switch plus a low-voltage power supply.  Conventional wisdom tells us that powering cameras via UTP cable also carrying data provides great cost savings.  Rarely, however, do we see costs comparisons from anyone but PoE manufacturers.  To that end, we examine the economics of various configurations of PoE and low-voltage power supplies.

Factors Driving Costs

To understand which offers lower costs, we must appreciate the factors driving cost and how they favor one approach vs the other.

The following factors favor PoE:

  • Eliminates secondary power cable. Since power can run over the UTP cable needed for video transmission, a PoE solution eliminates the cost of an 18/2 power cable. Specific savings will vary greatly depending on (1) the length of the cable needed and (2) the requirements for plenum. The longer the cable run and the more plenum is required, the greater the savings are for PoE. We estimate savings of $5 - $20 per camera.
  • Eliminates a conventional power supply. Since the network switch acts as a power supply, a PoE solution eliminates the need to purchase a low-voltage power supply. We estimate this saves $5 - $10 per camera.
  • Eliminates power cable termination. Since power runs over the the UTP cable needed for video transmission, no additional cable termination is required. We estimate this saves $12 - $25 per camera (assuming labor rates of $70-$100 and 10-20 minutes per termination).

The following factors favor low-voltage power:

  • Allows using a much lower cost switch. Adding PoE power to switches significantly increases the cost of the switch. We estimate savings of $20 - $25 per camera
  • (OR) Eliminates the use of a PoE midspan. PoE midspans can be quite expensive. We estimate $20 - $25 per camera.

Note: for any given IP camera using PoE, power will be provided by a switch (with PoE) or a midspan (not both simultaneously). The total cost reduction is $20 - $25 from one of these two options.

Less expensive PoE switches are available but they only provide 7.5 watts per port which can cause risk for many deployments when the average IP camera requires more than 7.5 watts (up to 15 watts).

Cost Savings Overview

We expect PoE power to save about $10 - $30 per camera over low voltage power supplies - a modest but real savings. Savings increase (to the higher end of this range) with longer cable runs and requirement for plenum (as conventional power requires an additional cable). These savings decrease with larger camera counts as conventional power supply costs become more cost effective with larger sizes (i.e. the per camera cost of a 16 camera power supply is much lower than an 8 camera power supply).

Detailed Equipment Cost Comparisons

For these comparisons, we chose the Cisco 300 series, the lowest cost member of their small business managed switch line.  Note that none of the 300 series switches used for comparison provide full PoE power to all ports.  Only a single 8-port model offers 15.4 watts on all ports, with all others offering only 7.5 watts.  This may be a problem, depending on the power draw of the camera.  For more information on calculating power budget, see our Powering Video Surveillance Report.

For power supplies, we chose Altronix, simply because they are well known as the industry leader, and readily available.  We will also examine the cost of utilizing a PoE midspan instead of a PoE switch, another common discussion in the industry.  Microsemi 3500 midspans (their most cost-effective line) were used for these comparisons.  

Cabling to each camera is assumed to be riser-rated, with an average length of 150’, and West Penn Wire (part numbers 224 and 4245) was used for pricing. 

Using the 300 series, the numbers look like this:

Eight Cameras

 

Non-PoE

PoE Switch

PoE Midspan

 Switch

$125 [link no longer available]

$225 [link no longer available]

$170

 Power Supply

$70

N/A

N/A

 18/2 Power Cable Plenum

$168

N/A

N/A

 Midspan

N/A

N/A

$450

 Cat 5e

$240

$240

$240

 Additional Labor

$150

$0

$30

 Total

$753

$465

$890

Note: additional labor is amount of labor costs above and beyond the simplest installation option - a PoE switch. Non-PoE will have the highest additional labor costs as cabling needs to be terminated for each camera to the low voltage power supply.

For 8 cameras, a cost savings of $293 in PoE’s favor (using a 7.5 Watt per port switch). Using a 15 watt per port network switch (the Cisco SF302-08MP runs about $300 [link no longer available]), the savings would reduce to about $220.

Sixteen Cameras

 

Non-PoE

PoE Switch

PoE Midspan

 Switch

$200

$400

$200

 Power Supply

$100

N/A

N/A

 Midspan

N/A

N/A

$800

 18/2 Power Cable Plenum

$336

N/A

N/A

 Cat 5e

$480

$480

$480

 Additional Labor

$300

$0

$40

 Total

$1,416

$880

$1,520

For 16 cameras, a cost savings of $536 in PoE’s favor for using a PoE Switch (remember though this is a 7.5 Watt per port solution). Moving to a switch which provides 15.4W across all ports requires moving to the Catalyst 2960 line, which comes at a $1,400+ premium.  This obviously makes lower-cost switches with midspans a more attractive option, especially when the other more advanced features of these switches are not required.

Other Factors to Consider

Considering that these are purely equipment and cable costs, PoE emerges as more cost-effective, with some key caveats: not every device will accept PoE power, and PoE will not necessarily provide enough power for every application.  PTZ cameras, cameras with heaters/blowers or IR illuminators, or other devices may require dedicated low-voltage cabling.  For more detailed information on power supply selection and application limitations, see our Powering Video Surveillance Report.Consider also that wall-mount power supplies were used, though rack-mount units are often preferred for neatness of installation and centralization of equipment.  With rack-mount power supplies often costing up to twice as much as a comparable wall-mount unit, the gap between PoE and low-voltage power supplies increases further.  PoE midspans drive up costs even further, above and beyond the pure equipment costs, in that they require an additional patch cord, and additional time to patch and manage cable in the rack.  We recommend carefully examining camera and switch specifications before simply determining PoE is best for your application.